bp2build: add allowlist for package-level conversions.

This CL adds the support for specifying lists of directories in
build/soong/android/bazel.go, which are then written into
out/soong/bp2build/MANIFEST. Using this configuration,
modules/directories can either default to bp2build_available: true or
false, while still retaining the ability to opt-in or out at the module level.

It also ensures that ConvertWithBp2Build returns true iff the module
type has a registered bp2build converter.

Test: go tests
Test: demo.sh full
Test: TreeHugger presubmits for bp2build and mixed builds.

Change-Id: I0e0f6f4b1b2ec045f2f1c338f7084defc5d23a55
diff --git a/bp2build/bp2build.go b/bp2build/bp2build.go
index 97a5137..007d6d8 100644
--- a/bp2build/bp2build.go
+++ b/bp2build/bp2build.go
@@ -18,44 +18,48 @@
 	"android/soong/android"
 	"fmt"
 	"os"
+	"strings"
 )
 
-// The Bazel bp2build code generator is responsible for writing .bzl files that are equivalent to
-// Android.bp files that are capable of being built with Bazel.
+// Codegen is the backend of bp2build. The code generator is responsible for
+// writing .bzl files that are equivalent to Android.bp files that are capable
+// of being built with Bazel.
 func Codegen(ctx *CodegenContext) CodegenMetrics {
 	outputDir := android.PathForOutput(ctx, "bp2build")
 	android.RemoveAllOutputDir(outputDir)
 
-	ruleShims := CreateRuleShims(android.ModuleTypeFactories())
-
 	buildToTargets, metrics := GenerateBazelTargets(ctx)
 
-	filesToWrite := CreateBazelFiles(ruleShims, buildToTargets, ctx.mode)
+	filesToWrite := CreateBazelFiles(nil, buildToTargets, ctx.mode)
+
+	generatedBuildFiles := []string{}
 	for _, f := range filesToWrite {
-		if err := writeFile(outputDir, ctx, f); err != nil {
+		p := getOrCreateOutputDir(outputDir, ctx, f.Dir).Join(ctx, f.Basename)
+		if err := writeFile(ctx, p, f.Contents); err != nil {
 			fmt.Errorf("Failed to write %q (dir %q) due to %q", f.Basename, f.Dir, err)
 		}
+		// if these generated files are modified, regenerate on next run.
+		generatedBuildFiles = append(generatedBuildFiles, p.String())
 	}
 
+	// The MANIFEST file contains the full list of files generated by bp2build, excluding itself.
+	// Its purpose is for downstream tools to understand the set of files converted by bp2build.
+	manifestFile := outputDir.Join(ctx, "MANIFEST")
+	writeFile(ctx, manifestFile, strings.Join(generatedBuildFiles, "\n"))
+	generatedBuildFiles = append(generatedBuildFiles, manifestFile.String())
+
 	return metrics
 }
 
-func writeFile(outputDir android.OutputPath, ctx android.PathContext, f BazelFile) error {
-	return writeReadOnlyFile(ctx, getOutputPath(outputDir, ctx, f.Dir), f.Basename, f.Contents)
+// Get the output directory and create it if it doesn't exist.
+func getOrCreateOutputDir(outputDir android.OutputPath, ctx android.PathContext, dir string) android.OutputPath {
+	dirPath := outputDir.Join(ctx, dir)
+	android.CreateOutputDirIfNonexistent(dirPath, os.ModePerm)
+	return dirPath
 }
 
-func getOutputPath(outputDir android.OutputPath, ctx android.PathContext, dir string) android.OutputPath {
-	return outputDir.Join(ctx, dir)
-}
-
-// The auto-conversion directory should be read-only, sufficient for bazel query. The files
-// are not intended to be edited by end users.
-func writeReadOnlyFile(ctx android.PathContext, dir android.OutputPath, baseName, content string) error {
-	android.CreateOutputDirIfNonexistent(dir, os.ModePerm)
-	pathToFile := dir.Join(ctx, baseName)
-
-	// 0444 is read-only
-	err := android.WriteFileToOutputDir(pathToFile, []byte(content), 0444)
-
-	return err
+func writeFile(ctx android.PathContext, pathToFile android.OutputPath, content string) error {
+	// These files are made editable to allow users to modify and iterate on them
+	// in the source tree.
+	return android.WriteFileToOutputDir(pathToFile, []byte(content), 0644)
 }
diff --git a/bp2build/build_conversion_test.go b/bp2build/build_conversion_test.go
index 89acbe9..b9b250a 100644
--- a/bp2build/build_conversion_test.go
+++ b/bp2build/build_conversion_test.go
@@ -412,7 +412,7 @@
 		config := android.TestConfig(buildDir, nil, testCase.bp, nil)
 		ctx := android.NewTestContext(config)
 		ctx.RegisterModuleType("custom", customModuleFactory)
-		ctx.RegisterBp2BuildMutator("custom_starlark", customBp2BuildMutatorFromStarlark)
+		ctx.RegisterBp2BuildMutator("custom", customBp2BuildMutatorFromStarlark)
 		ctx.RegisterForBazelConversion()
 
 		_, errs := ctx.ParseFileList(dir, []string{"Android.bp"})
@@ -1144,7 +1144,7 @@
 	}
 }
 
-func TestAllowlistingBp2buildTargets(t *testing.T) {
+func TestAllowlistingBp2buildTargetsExplicitly(t *testing.T) {
 	testCases := []struct {
 		moduleTypeUnderTest                string
 		moduleTypeUnderTestFactory         android.ModuleFactory
@@ -1222,6 +1222,124 @@
 	}
 }
 
+func TestAllowlistingBp2buildTargetsWithConfig(t *testing.T) {
+	testCases := []struct {
+		moduleTypeUnderTest                string
+		moduleTypeUnderTestFactory         android.ModuleFactory
+		moduleTypeUnderTestBp2BuildMutator bp2buildMutator
+		expectedCount                      map[string]int
+		description                        string
+		bp2buildConfig                     android.Bp2BuildConfig
+		checkDir                           string
+		fs                                 map[string]string
+	}{
+		{
+			description:                        "test bp2build config package and subpackages config",
+			moduleTypeUnderTest:                "filegroup",
+			moduleTypeUnderTestFactory:         android.FileGroupFactory,
+			moduleTypeUnderTestBp2BuildMutator: android.FilegroupBp2Build,
+			expectedCount: map[string]int{
+				"migrated":                           1,
+				"migrated/but_not_really":            0,
+				"migrated/but_not_really/but_really": 1,
+				"not_migrated":                       0,
+				"also_not_migrated":                  0,
+			},
+			bp2buildConfig: android.Bp2BuildConfig{
+				"migrated":                android.Bp2BuildDefaultTrueRecursively,
+				"migrated/but_not_really": android.Bp2BuildDefaultFalse,
+				"not_migrated":            android.Bp2BuildDefaultFalse,
+			},
+			fs: map[string]string{
+				"migrated/Android.bp":                           `filegroup { name: "a" }`,
+				"migrated/but_not_really/Android.bp":            `filegroup { name: "b" }`,
+				"migrated/but_not_really/but_really/Android.bp": `filegroup { name: "c" }`,
+				"not_migrated/Android.bp":                       `filegroup { name: "d" }`,
+				"also_not_migrated/Android.bp":                  `filegroup { name: "e" }`,
+			},
+		},
+		{
+			description:                        "test bp2build config opt-in and opt-out",
+			moduleTypeUnderTest:                "filegroup",
+			moduleTypeUnderTestFactory:         android.FileGroupFactory,
+			moduleTypeUnderTestBp2BuildMutator: android.FilegroupBp2Build,
+			expectedCount: map[string]int{
+				"package-opt-in":             2,
+				"package-opt-in/subpackage":  0,
+				"package-opt-out":            1,
+				"package-opt-out/subpackage": 0,
+			},
+			bp2buildConfig: android.Bp2BuildConfig{
+				"package-opt-in":  android.Bp2BuildDefaultFalse,
+				"package-opt-out": android.Bp2BuildDefaultTrueRecursively,
+			},
+			fs: map[string]string{
+				"package-opt-in/Android.bp": `
+filegroup { name: "opt-in-a" }
+filegroup { name: "opt-in-b", bazel_module: { bp2build_available: true } }
+filegroup { name: "opt-in-c", bazel_module: { bp2build_available: true } }
+`,
+
+				"package-opt-in/subpackage/Android.bp": `
+filegroup { name: "opt-in-d" } // parent package not configured to DefaultTrueRecursively
+`,
+
+				"package-opt-out/Android.bp": `
+filegroup { name: "opt-out-a" }
+filegroup { name: "opt-out-b", bazel_module: { bp2build_available: false } }
+filegroup { name: "opt-out-c", bazel_module: { bp2build_available: false } }
+`,
+
+				"package-opt-out/subpackage/Android.bp": `
+filegroup { name: "opt-out-g", bazel_module: { bp2build_available: false } }
+filegroup { name: "opt-out-h", bazel_module: { bp2build_available: false } }
+`,
+			},
+		},
+	}
+
+	dir := "."
+	for _, testCase := range testCases {
+		fs := make(map[string][]byte)
+		toParse := []string{
+			"Android.bp",
+		}
+		for f, content := range testCase.fs {
+			if strings.HasSuffix(f, "Android.bp") {
+				toParse = append(toParse, f)
+			}
+			fs[f] = []byte(content)
+		}
+		config := android.TestConfig(buildDir, nil, "", fs)
+		ctx := android.NewTestContext(config)
+		ctx.RegisterModuleType(testCase.moduleTypeUnderTest, testCase.moduleTypeUnderTestFactory)
+		ctx.RegisterBp2BuildMutator(testCase.moduleTypeUnderTest, testCase.moduleTypeUnderTestBp2BuildMutator)
+		ctx.RegisterBp2BuildConfig(testCase.bp2buildConfig)
+		ctx.RegisterForBazelConversion()
+
+		_, errs := ctx.ParseFileList(dir, toParse)
+		android.FailIfErrored(t, errs)
+		_, errs = ctx.ResolveDependencies(config)
+		android.FailIfErrored(t, errs)
+
+		codegenCtx := NewCodegenContext(config, *ctx.Context, Bp2Build)
+
+		// For each directory, test that the expected number of generated targets is correct.
+		for dir, expectedCount := range testCase.expectedCount {
+			bazelTargets := generateBazelTargetsForDir(codegenCtx, dir)
+			if actualCount := len(bazelTargets); actualCount != expectedCount {
+				t.Fatalf(
+					"%s: Expected %d bazel target for %s package, got %d",
+					testCase.description,
+					expectedCount,
+					dir,
+					actualCount)
+			}
+
+		}
+	}
+}
+
 func TestCombineBuildFilesBp2buildTargets(t *testing.T) {
 	testCases := []struct {
 		description                        string
diff --git a/bp2build/conversion.go b/bp2build/conversion.go
index 7877bb8..787222d 100644
--- a/bp2build/conversion.go
+++ b/bp2build/conversion.go
@@ -21,14 +21,15 @@
 	mode CodegenMode) []BazelFile {
 	files := make([]BazelFile, 0, len(ruleShims)+len(buildToTargets)+numAdditionalFiles)
 
-	// Write top level files: WORKSPACE and BUILD. These files are empty.
+	// Write top level files: WORKSPACE. These files are empty.
 	files = append(files, newFile("", "WORKSPACE", ""))
-	// Used to denote that the top level directory is a package.
-	files = append(files, newFile("", GeneratedBuildFileName, ""))
-
-	files = append(files, newFile(bazelRulesSubDir, GeneratedBuildFileName, ""))
 
 	if mode == QueryView {
+		// Used to denote that the top level directory is a package.
+		files = append(files, newFile("", GeneratedBuildFileName, ""))
+
+		files = append(files, newFile(bazelRulesSubDir, GeneratedBuildFileName, ""))
+
 		// These files are only used for queryview.
 		files = append(files, newFile(bazelRulesSubDir, "providers.bzl", providersBzl))
 
diff --git a/bp2build/conversion_test.go b/bp2build/conversion_test.go
index ec5f27e..a115ddc 100644
--- a/bp2build/conversion_test.go
+++ b/bp2build/conversion_test.go
@@ -89,16 +89,8 @@
 	expectedFilePaths := []filepath{
 		{
 			dir:      "",
-			basename: "BUILD",
-		},
-		{
-			dir:      "",
 			basename: "WORKSPACE",
 		},
-		{
-			dir:      bazelRulesSubDir,
-			basename: "BUILD",
-		},
 	}
 
 	assertFilecountsAreEqual(t, files, expectedFilePaths)
diff --git a/bp2build/testing.go b/bp2build/testing.go
index a15a4a5..ede8044 100644
--- a/bp2build/testing.go
+++ b/bp2build/testing.go
@@ -126,7 +126,7 @@
 
 func customBp2BuildMutator(ctx android.TopDownMutatorContext) {
 	if m, ok := ctx.Module().(*customModule); ok {
-		if !m.ConvertWithBp2build() {
+		if !m.ConvertWithBp2build(ctx) {
 			return
 		}
 
@@ -147,7 +147,7 @@
 // module to target.
 func customBp2BuildMutatorFromStarlark(ctx android.TopDownMutatorContext) {
 	if m, ok := ctx.Module().(*customModule); ok {
-		if !m.ConvertWithBp2build() {
+		if !m.ConvertWithBp2build(ctx) {
 			return
 		}